Self-controlled signal branch by the use of a nonlinear liquid crystal cell

A nonlinear input-output characteristic was observed when neodymium doped yttrium aluminum garnet laser passed through a silicon cell containing a twisted-nematic liquid crystal. The laser beam excited free carriers in the silicon plate, which triggered electrical reorientation of the liquid crystal. Consequently, the polarization direction of the laser beam changed, and the output beam passing through a polarizer became weaker as the input power increased. This function was utilized for self-branching of an optical pulse train.